Wireless communication systems typically have a base station or access point from which radio signals are transmitted and propagate. These signals are then received by a mobile station, remote station, user station, client station, subscriber station, etcetera (referred to herein collectively as stations) allowing communication to proceed. Stations may be, for example, a computer with a wireless modem such as a notebook computer fitted with a wireless local area network (WLAN) card (referred to herein as a wireless notebook), mobile telephone or a wireless personal digital assistant.
Wireless communication systems typically provide two-way or duplex communication so that an access point can exchange data with or “talk” to a station, such as a wireless notebook, and the station can exchange data with or “talk” to the access point. In effect, there are two separate radio links by which these two signals travel, known respectively as the down-link and up-link.
Radio frequency (RF) signals can only propagate a certain distance through a medium, such as air, before their power level is appreciably attenuated. For example, there is a distance from a transmission source (e.g., transmitting antenna) at which the RF signal level falls below a certain threshold and cannot be usefully received. The area around a network access point in which signals can be usefully received is known as the coverage area and is sometimes referred to as a cell. When a station moves outside the coverage area, signals cannot be usefully received and communication is generally not possible. Accordingly it is often desirable to implement wireless systems that create as large a network coverage area as possible at minimum cost in order to provide communication services to as large an areas, and thus as many stations, as possible.
Recently, wireless communications have been combined with local area network (LAN) systems to provide wireless LAN (WLAN) configurations in which stations may be freely distributed throughout a workspace, e.g., an office building, and provided with high bandwidth data communications (such as on the order of 10 to 54 mega-bits per second (Mbps)) without a network cable attached to the stations. Accordingly, WLAN infrastructure has been designed for indoor pedestrian (ambulatory mobility) access over relatively short distances (e.g., on the order of 1-30 meters).
It is a challenging problem to extend the coverage area of a WLAN system to provide high bandwidth coverage in outdoor public areas or other large coverage areas. For example, hidden node problems (e.g., where a first station is within the communication area of an AP and can communicate with the AP, a second station is also within the communication area of an AP and can communicate with the AP, but the first and second station are disposed such that they cannot detect each other's communications) may be increased. Likewise, interference, whether intra-cell, inter-cell, and external, may be aggravated through extending a WLAN coverage area.
Accordingly, there is a need for a system and method for providing relatively high bandwidth data communication in a large coverage area, such as a macrocell having a radius on the order of 500 meters or more. There is a further need for a system and method for extending a coverage area of WLAN infrastructure to provide WLAN data communication in a large coverage area.